The invention relates to an array-based C-MOS sensor device that is provided with a facility for on the basis of non-destructive cell readout generating a radiation dose-sensing signal as being recited in the preamble of Claim 1. It is to be noted that in this application C-MOS sensor means that the sensor is based on CMOS (=Complimentary Metal Oxide Semiconductor) technology or on NMOS technology or on PMOS technology. In CMOS technology both NMOS and PMOS technology is used.
Such sensors have been in use for imaging transmission patterns from ionizing radiation, that without limitation are used in medical diagnostics. Dosage determination is essential, because applying too little radiation will result in unclear and/or faulty images produced. On the other hand, extending the time of irradiating too much can have a negative influence on the health of a subject that is irradiated, or other unwanted effects.
Prior art, in particular U.S. Pat. No. 5,887,049 to Fossum uses a plurality of specific edge detector elements in C-MOS technology to activate the pixel array for so producing a self-triggered X-ray sensor. In contradistinction, the present inventors have recognized that with presently advanced technology it would be feasible to distribute the detector cells across the array without negatively influencing the operation of the overall array. For one, generally in medical applications the effective cell pitch can be relatively much larger than would be actually attainable through state-of-the-art technology. Larger cells allow to assign to certain selected cells inside the array a specific readout facility for control purposes, such as represented by an extra transistor and/or additional wiring.
On the other hand, the present inventors have recognized that non-destructive read-out of the whole of a multi-cell array requires much time and complicated access operations. Therefore, readout out of a relatively small subset of the overall array would allow to produce a fast, simple and low-energy means for signaling actual exposure of the array.